Aromatic aramid commonly called aramid includes para-aramid with a structure of benzene rings straightly linked through amide group (CONH) and meta-aramid without the same.
The para-aramid has high strength, high elasticity and low shrinkage or the like. Since a fine thread or string having a thickness of about 5 mm fabricated using the para-aramid has an extremely high strength enough to lift up an automobile of about 2 tons in weight, it is used for bombproof applications and further employed in various uses in high-technology industries in the field of aerospace industry.
The para-aramid is carbonized to become black at a temperature of 500° C. or higher, thus being highlighted in specific applications with a necessity of high thermal resistance.
A method of manufacturing para-aramid fiber has been described well in Korean Patent Registration No. 10-0910537 owned by the present applicant. According to the registered patent, an aramid polymer is prepared by dissolving aromatic diamine in a polymerization solvent to prepare a mixed solution and adding aromatic diacid thereto. After dissolving the aramid polymer in a sulfuric acid solvent to form a spin dope and spinning the same, coagulation, washing and drying are sequentially conducted to finally manufacture the aramid fiber.
However, according to the method of manufacturing the para-aramid fiber by the foregoing processes, the spin dope is formed by firstly preparing a solid para-aramid polymer and dissolving it in a sulfuric acid solvent, and then, subjected to spinning. Accordingly, the foregoing method needs relatively complicated processes, is harmful to health, and problems such as a decrease in durability due to corrosion of apparatus may be entailed.
Further, the sulfuric acid solvent used to dissolve the para-aramid polymer having a high chemical resistance and removed after spinning causes environmental pollution, therefore, must be appropriately treated after use. However, costs necessary for treatment of sulfuric acid waste may result in deterioration of economic efficiency.
Furthermore, according to the above related art, a spin dope formed by dissolving a para-aramid polymer in a sulfuric acid solvent is spun in a fibrous form through a spinneret, and the spun fiber is processed in a wet spinning manner such that the fiber passes through an air gap, followed by passing through a coagulant solution in a coagulation bath. Consequently, there is still a problem of requiring a great amount of energy and huge costs.